AMOLED (Active-matrix organic light-emitting diode) is a kind of display technologies applied in televisions and mobile devices. A display screen using the AMOLED technology obtains favor of various customers and is well received, and at the same time, a next AMOLED display technology related to low temperature poly-silicon liquid crystal display (LTPS-LCD) has been developed.
Compared with a traditional display technology, the AMOLED has the following advantages:
1. Compared with a liquid crystal box technology of the traditional LCD, the AMOLED dose not need liquid crystals, and can achieve self-luminance only through a very thin organic light-emitting layer, and therefore the AMOLED can be lighter and thinner, and in a market where an ultra-thin machine needs to be lighter and thinner, the AMOLED has an insurmountable advantage;
2. The AMOLED can break through restriction of the traditional RGB pixel arrangement, can implement a pentle pixel structure and achieve an effect of a high resolution;
3. The AMOLED achieves a display function by adopting the principle of self-luminance; when an image shows black, pixels do not need to illuminate, while the LCD is also in a working state when showing black; and so by comparison, the AMOLED can not only achieve a high contrast, but also can reduce power consumption to achieve an effect of saving electricity;
4. The AMOLED can realize flexible display; by using a special technology, a circuit of the AMOLED can be implemented on a flexible substrate to realize flexible display;
5. The AMOLED and a SUPER AMOLED have very wide color gamut, but have color deviation.
However, the AMOLED as a high-end display technology have strict requirements on a manufacturing process. There are difficulties from the manufacturing of a driving circuit to subsequent evaporating of an organic light emitting layer, which is the reason why at the present stage, breaking the manufacturing yield of the AMOLED is a difficult problem which is needed to be considered.
OLED refers to a phenomenon that, under the driving of an electric field, a semiconductor material and a luminescent material lead to light emission through the carrier injection and recombination. The luminescence principle of the OLED includes: by adopting an indium tin oxides (ITO) transparent electrode and a metal electrode as an anode and a cathode respectively, under a certain driving voltage, electrons and holes are injected from the cathode and the anode into an electron transport layer and a hole transport layer respectively, the electrons and the holes migrate through the electron transport layer and the hole transport layer respectively to a light emitting layer, and meet in the light emitting layer to form excitons and excite the luminescent molecules, and the luminescent molecules emit visible light through radiative relaxation. The radiation light can be observed from the side of the ITO, and the metal electrode film also acts as a reflector.
Apparently, it is completely different from the luminescence mechanism of a twisted nematic (TN) display technology. The two types of panels adopt different light sources. The OLED (Organic Light-Emitting Diode) emits light by self, and the TN display adopts a backlight source. By contrast it is not difficult to find that the OLED has advantages such as thinner and lighter, active luminescence (no backlight source), no viewing angle problem, high definition, high brightness, fast response, low power consumption, wide usage temperature range, strong anti-shock capacity, low cost and flexible display, etc., where many of these features are difficult to achieve by a thin film transistor (TFT) liquid crystal panel.
The OLED describes an organic electroluminescent display which is a specific type of the thin film display technology. AM (active matrix) refers to a pixel addressing technology. The characteristic of self-luminance of the AMOLED leads to a key influence of the driving circuit for the light uniformity. In the present driving circuit, threshold voltages of driving thin film transistors which each drive a light emitting diode in each pixel are not uniform, which leads that even if the driving voltages applied to each driving thin film transistor are the same, the current flowing through each OLED may be different, so as to affect display effects.